The Dunedin City Council will be taking a ''highly cautious'' approach during a 1080 drop in an area used as a back-up treated water supply.

The council announced yesterday it had approved a request from Ospri to undertake pest control on council land in the Silverstream catchment next month.​The council said its cautious approach to the drop included not taking water from the catchment while 1080 was present, closing tracks for 15 days, and not allowing dogs in the area for up to a year.

The 1080 drop would be the first in the Silverstream catchment and was likely to begin on or after June 5 and also take place on some Department of Conservation and privately-owned land north of the area.

The operation is part of Ospri's TBfree New Zealand programme to control and eradicate bovine Tb in possums.

Council chief executive Sue Bidrose said the council gave serious consideration to the proposal before permission was granted.

''Ospri has a national responsibility to conduct pest control work to prevent the spread of Tb and works with landowners for permission.

Since the request was made our focus has been on ensuring that we put in place all possible precautions, more than bare minimum requirements, to ensure that the drop is done safely,'' Dr Bidrose said.

The operation was part of a national programme and fitted with the Government's goal of a predator-free New Zealand by 2050.

''This operation targets possums, but will also reduce the number of rats and other predators. It will remove threats to our native bird species and biodiversity, giving them a better chance of survival and helping them to flourish.''

Acting parks and recreation manager Tom Dyer said the council had been working with Ospri and there were strict policies around 1080 use.

''A highly cautious approach is being taken so no drinking water will be used from the Silverstream while 1080 is present,'' Mr Dyer said.

The operation would also impact on recreational users.

''The catchment and affected tracks will be closed to all users for around 15 days.''

After that the reserve would reopen to the general public, but remain closed to dogs for up to a year.

Hunting permits for the catchment would also be suspended to ensure dog safety.

''Alternative off-lead walking tracks have been identified and will be promoted to dog owners.

''We're working to ensure all users are informed about this.''

The operation was weather-dependent and would take about two weeks.

Ospri would signpost affected areas and information would be available on the council website.

An Ospri spokesman said to eradicate bovine Tb, possum numbers needed to be kept ''extremely low'' at about one to two animals every 10ha.

Monitoring had shown further control work was needed in the Silver Peaks area to reduce the possum population and minimise the risk of the disease spreading through wild animal populations and on to farmed cattle and deer.

The Silver Peaks part of the block was last aerially treated in 2011, while the Silverstream portion had never received aerial drops of 1080.

''We tried for a number of years to complete ground control in the Silverstream area and it was extremely expensive and not as effective when compared to aerial.''